gecko-dev/xpcom/threads/LazyIdleThread.cpp
Andreas Farre d87b4d239b Bug 1198381 - Extend nsIThread with idleDispatch, r=froydnj,smaug
The intent of idleDispatch is the possibility to have a runnable
executed when the thread is idle. This is accomplished by adding an
event queue for idle tasks that will only be considered when the main
event queue is empty and the caller of ProcessNextEvent doesn't
require that we wait until there is an event on the main event queue.

MozReview-Commit-ID: IDWQfzZqWpZ

--HG--
extra : rebase_source : 0d5bfeebd08e01597c2cd8b76e8e848d9f9c58f0
2016-08-24 16:18:06 +02:00

625 lines
15 KiB
C++

/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
#include "LazyIdleThread.h"
#include "nsIObserverService.h"
#include "GeckoProfiler.h"
#include "nsComponentManagerUtils.h"
#include "nsIIdlePeriod.h"
#include "nsServiceManagerUtils.h"
#include "nsThreadUtils.h"
#include "mozilla/Services.h"
#ifdef DEBUG
#define ASSERT_OWNING_THREAD() \
PR_BEGIN_MACRO \
nsIThread* currentThread = NS_GetCurrentThread(); \
if (currentThread) { \
nsCOMPtr<nsISupports> current(do_QueryInterface(currentThread)); \
nsCOMPtr<nsISupports> test(do_QueryInterface(mOwningThread)); \
MOZ_ASSERT(current == test, "Wrong thread!"); \
} \
PR_END_MACRO
#else
#define ASSERT_OWNING_THREAD() /* nothing */
#endif
namespace mozilla {
LazyIdleThread::LazyIdleThread(uint32_t aIdleTimeoutMS,
const nsCSubstring& aName,
ShutdownMethod aShutdownMethod,
nsIObserver* aIdleObserver)
: mMutex("LazyIdleThread::mMutex")
, mOwningThread(NS_GetCurrentThread())
, mIdleObserver(aIdleObserver)
, mQueuedRunnables(nullptr)
, mIdleTimeoutMS(aIdleTimeoutMS)
, mPendingEventCount(0)
, mIdleNotificationCount(0)
, mShutdownMethod(aShutdownMethod)
, mShutdown(false)
, mThreadIsShuttingDown(false)
, mIdleTimeoutEnabled(true)
, mName(aName)
{
MOZ_ASSERT(mOwningThread, "Need owning thread!");
}
LazyIdleThread::~LazyIdleThread()
{
ASSERT_OWNING_THREAD();
Shutdown();
}
void
LazyIdleThread::SetWeakIdleObserver(nsIObserver* aObserver)
{
ASSERT_OWNING_THREAD();
if (mShutdown) {
NS_WARNING_ASSERTION(!aObserver,
"Setting an observer after Shutdown was called!");
return;
}
mIdleObserver = aObserver;
}
void
LazyIdleThread::DisableIdleTimeout()
{
ASSERT_OWNING_THREAD();
if (!mIdleTimeoutEnabled) {
return;
}
mIdleTimeoutEnabled = false;
if (mIdleTimer && NS_FAILED(mIdleTimer->Cancel())) {
NS_WARNING("Failed to cancel timer!");
}
MutexAutoLock lock(mMutex);
// Pretend we have a pending event to keep the idle timer from firing.
MOZ_ASSERT(mPendingEventCount < UINT32_MAX, "Way too many!");
mPendingEventCount++;
}
void
LazyIdleThread::EnableIdleTimeout()
{
ASSERT_OWNING_THREAD();
if (mIdleTimeoutEnabled) {
return;
}
mIdleTimeoutEnabled = true;
{
MutexAutoLock lock(mMutex);
MOZ_ASSERT(mPendingEventCount, "Mismatched calls to observer methods!");
--mPendingEventCount;
}
if (mThread) {
nsCOMPtr<nsIRunnable> runnable(new Runnable());
if (NS_FAILED(Dispatch(runnable.forget(), NS_DISPATCH_NORMAL))) {
NS_WARNING("Failed to dispatch!");
}
}
}
void
LazyIdleThread::PreDispatch()
{
MutexAutoLock lock(mMutex);
MOZ_ASSERT(mPendingEventCount < UINT32_MAX, "Way too many!");
mPendingEventCount++;
}
nsresult
LazyIdleThread::EnsureThread()
{
ASSERT_OWNING_THREAD();
if (mShutdown) {
return NS_ERROR_UNEXPECTED;
}
if (mThread) {
return NS_OK;
}
MOZ_ASSERT(!mPendingEventCount, "Shouldn't have events yet!");
MOZ_ASSERT(!mIdleNotificationCount, "Shouldn't have idle events yet!");
MOZ_ASSERT(!mIdleTimer, "Should have killed this long ago!");
MOZ_ASSERT(!mThreadIsShuttingDown, "Should have cleared that!");
nsresult rv;
if (mShutdownMethod == AutomaticShutdown && NS_IsMainThread()) {
nsCOMPtr<nsIObserverService> obs =
do_GetService(NS_OBSERVERSERVICE_CONTRACTID, &rv);
if (NS_WARN_IF(NS_FAILED(rv))) {
return rv;
}
rv = obs->AddObserver(this, "xpcom-shutdown-threads", false);
if (NS_WARN_IF(NS_FAILED(rv))) {
return rv;
}
}
mIdleTimer = do_CreateInstance(NS_TIMER_CONTRACTID, &rv);
if (NS_WARN_IF(!mIdleTimer)) {
return NS_ERROR_UNEXPECTED;
}
nsCOMPtr<nsIRunnable> runnable =
NewRunnableMethod(this, &LazyIdleThread::InitThread);
if (NS_WARN_IF(!runnable)) {
return NS_ERROR_UNEXPECTED;
}
rv = NS_NewThread(getter_AddRefs(mThread), runnable);
if (NS_WARN_IF(NS_FAILED(rv))) {
return rv;
}
return NS_OK;
}
void
LazyIdleThread::InitThread()
{
char aLocal;
profiler_register_thread(mName.get(), &aLocal);
PR_SetCurrentThreadName(mName.get());
// Happens on mThread but mThread may not be set yet...
nsCOMPtr<nsIThreadInternal> thread(do_QueryInterface(NS_GetCurrentThread()));
MOZ_ASSERT(thread, "This should always succeed!");
if (NS_FAILED(thread->SetObserver(this))) {
NS_WARNING("Failed to set thread observer!");
}
}
void
LazyIdleThread::CleanupThread()
{
nsCOMPtr<nsIThreadInternal> thread(do_QueryInterface(NS_GetCurrentThread()));
MOZ_ASSERT(thread, "This should always succeed!");
if (NS_FAILED(thread->SetObserver(nullptr))) {
NS_WARNING("Failed to set thread observer!");
}
{
MutexAutoLock lock(mMutex);
MOZ_ASSERT(!mThreadIsShuttingDown, "Shouldn't be true ever!");
mThreadIsShuttingDown = true;
}
profiler_unregister_thread();
}
void
LazyIdleThread::ScheduleTimer()
{
ASSERT_OWNING_THREAD();
bool shouldSchedule;
{
MutexAutoLock lock(mMutex);
MOZ_ASSERT(mIdleNotificationCount, "Should have at least one!");
--mIdleNotificationCount;
shouldSchedule = !mIdleNotificationCount && !mPendingEventCount;
}
if (mIdleTimer) {
if (NS_FAILED(mIdleTimer->Cancel())) {
NS_WARNING("Failed to cancel timer!");
}
if (shouldSchedule &&
NS_FAILED(mIdleTimer->InitWithCallback(this, mIdleTimeoutMS,
nsITimer::TYPE_ONE_SHOT))) {
NS_WARNING("Failed to schedule timer!");
}
}
}
nsresult
LazyIdleThread::ShutdownThread()
{
ASSERT_OWNING_THREAD();
// Before calling Shutdown() on the real thread we need to put a queue in
// place in case a runnable is posted to the thread while it's in the
// process of shutting down. This will be our queue.
AutoTArray<nsCOMPtr<nsIRunnable>, 10> queuedRunnables;
nsresult rv;
// Make sure to cancel the shutdown timer before spinning the event loop
// during |mThread->Shutdown()| below. Otherwise the timer might fire and we
// could reenter here.
if (mIdleTimer) {
rv = mIdleTimer->Cancel();
if (NS_WARN_IF(NS_FAILED(rv))) {
return rv;
}
mIdleTimer = nullptr;
}
if (mThread) {
if (mShutdownMethod == AutomaticShutdown && NS_IsMainThread()) {
nsCOMPtr<nsIObserverService> obs =
mozilla::services::GetObserverService();
NS_WARNING_ASSERTION(obs, "Failed to get observer service!");
if (obs &&
NS_FAILED(obs->RemoveObserver(this, "xpcom-shutdown-threads"))) {
NS_WARNING("Failed to remove observer!");
}
}
if (mIdleObserver) {
mIdleObserver->Observe(static_cast<nsIThread*>(this), IDLE_THREAD_TOPIC,
nullptr);
}
#ifdef DEBUG
{
MutexAutoLock lock(mMutex);
MOZ_ASSERT(!mThreadIsShuttingDown, "Huh?!");
}
#endif
nsCOMPtr<nsIRunnable> runnable =
NewRunnableMethod(this, &LazyIdleThread::CleanupThread);
if (NS_WARN_IF(!runnable)) {
return NS_ERROR_UNEXPECTED;
}
PreDispatch();
rv = mThread->Dispatch(runnable.forget(), NS_DISPATCH_NORMAL);
if (NS_WARN_IF(NS_FAILED(rv))) {
return rv;
}
// Put the temporary queue in place before calling Shutdown().
mQueuedRunnables = &queuedRunnables;
if (NS_FAILED(mThread->Shutdown())) {
NS_ERROR("Failed to shutdown the thread!");
}
// Now unset the queue.
mQueuedRunnables = nullptr;
mThread = nullptr;
{
MutexAutoLock lock(mMutex);
MOZ_ASSERT(!mPendingEventCount, "Huh?!");
MOZ_ASSERT(!mIdleNotificationCount, "Huh?!");
MOZ_ASSERT(mThreadIsShuttingDown, "Huh?!");
mThreadIsShuttingDown = false;
}
}
// If our temporary queue has any runnables then we need to dispatch them.
if (queuedRunnables.Length()) {
// If the thread manager has gone away then these runnables will never run.
if (mShutdown) {
NS_ERROR("Runnables dispatched to LazyIdleThread will never run!");
return NS_OK;
}
// Re-dispatch the queued runnables.
for (uint32_t index = 0; index < queuedRunnables.Length(); index++) {
nsCOMPtr<nsIRunnable> runnable;
runnable.swap(queuedRunnables[index]);
MOZ_ASSERT(runnable, "Null runnable?!");
if (NS_FAILED(Dispatch(runnable.forget(), NS_DISPATCH_NORMAL))) {
NS_ERROR("Failed to re-dispatch queued runnable!");
}
}
}
return NS_OK;
}
void
LazyIdleThread::SelfDestruct()
{
MOZ_ASSERT(mRefCnt == 1, "Bad refcount!");
delete this;
}
NS_IMPL_ADDREF(LazyIdleThread)
NS_IMETHODIMP_(MozExternalRefCountType)
LazyIdleThread::Release()
{
nsrefcnt count = --mRefCnt;
NS_LOG_RELEASE(this, count, "LazyIdleThread");
if (!count) {
// Stabilize refcount.
mRefCnt = 1;
nsCOMPtr<nsIRunnable> runnable =
NewNonOwningRunnableMethod(this, &LazyIdleThread::SelfDestruct);
NS_WARNING_ASSERTION(runnable, "Couldn't make runnable!");
if (NS_FAILED(NS_DispatchToCurrentThread(runnable))) {
MOZ_ASSERT(NS_IsMainThread(), "Wrong thread!");
// The only way this could fail is if we're in shutdown, and in that case
// threads should have been joined already. Deleting here isn't dangerous
// anymore because we won't spin the event loop waiting to join the
// thread.
SelfDestruct();
}
}
return count;
}
NS_IMPL_QUERY_INTERFACE(LazyIdleThread, nsIThread,
nsIEventTarget,
nsITimerCallback,
nsIThreadObserver,
nsIObserver)
NS_IMETHODIMP
LazyIdleThread::DispatchFromScript(nsIRunnable* aEvent, uint32_t aFlags)
{
nsCOMPtr<nsIRunnable> event(aEvent);
return Dispatch(event.forget(), aFlags);
}
NS_IMETHODIMP
LazyIdleThread::Dispatch(already_AddRefed<nsIRunnable> aEvent,
uint32_t aFlags)
{
ASSERT_OWNING_THREAD();
nsCOMPtr<nsIRunnable> event(aEvent); // avoid leaks
// LazyIdleThread can't always support synchronous dispatch currently.
if (NS_WARN_IF(aFlags != NS_DISPATCH_NORMAL)) {
return NS_ERROR_NOT_IMPLEMENTED;
}
if (NS_WARN_IF(mShutdown)) {
return NS_ERROR_UNEXPECTED;
}
// If our thread is shutting down then we can't actually dispatch right now.
// Queue this runnable for later.
if (UseRunnableQueue()) {
mQueuedRunnables->AppendElement(event);
return NS_OK;
}
nsresult rv = EnsureThread();
if (NS_WARN_IF(NS_FAILED(rv))) {
return rv;
}
PreDispatch();
return mThread->Dispatch(event.forget(), aFlags);
}
NS_IMETHODIMP
LazyIdleThread::DelayedDispatch(already_AddRefed<nsIRunnable>, uint32_t)
{
return NS_ERROR_NOT_IMPLEMENTED;
}
NS_IMETHODIMP
LazyIdleThread::IsOnCurrentThread(bool* aIsOnCurrentThread)
{
if (mThread) {
return mThread->IsOnCurrentThread(aIsOnCurrentThread);
}
*aIsOnCurrentThread = false;
return NS_OK;
}
NS_IMETHODIMP
LazyIdleThread::GetPRThread(PRThread** aPRThread)
{
if (mThread) {
return mThread->GetPRThread(aPRThread);
}
*aPRThread = nullptr;
return NS_ERROR_NOT_AVAILABLE;
}
NS_IMETHODIMP
LazyIdleThread::GetCanInvokeJS(bool* aCanInvokeJS)
{
*aCanInvokeJS = false;
return NS_OK;
}
NS_IMETHODIMP
LazyIdleThread::SetCanInvokeJS(bool aCanInvokeJS)
{
return NS_ERROR_NOT_IMPLEMENTED;
}
NS_IMETHODIMP
LazyIdleThread::AsyncShutdown()
{
ASSERT_OWNING_THREAD();
return NS_ERROR_NOT_IMPLEMENTED;
}
NS_IMETHODIMP
LazyIdleThread::Shutdown()
{
ASSERT_OWNING_THREAD();
mShutdown = true;
nsresult rv = ShutdownThread();
MOZ_ASSERT(!mThread, "Should have destroyed this by now!");
mIdleObserver = nullptr;
if (NS_WARN_IF(NS_FAILED(rv))) {
return rv;
}
return NS_OK;
}
NS_IMETHODIMP
LazyIdleThread::HasPendingEvents(bool* aHasPendingEvents)
{
// This is only supposed to be called from the thread itself so it's not
// implemented here.
NS_NOTREACHED("Shouldn't ever call this!");
return NS_ERROR_UNEXPECTED;
}
NS_IMETHODIMP
LazyIdleThread::IdleDispatch(already_AddRefed<nsIRunnable> aEvent)
{
return NS_ERROR_NOT_IMPLEMENTED;
}
NS_IMETHODIMP
LazyIdleThread::RegisterIdlePeriod(already_AddRefed<nsIIdlePeriod> aIdlePeriod)
{
return NS_ERROR_NOT_IMPLEMENTED;
}
NS_IMETHODIMP
LazyIdleThread::ProcessNextEvent(bool aMayWait,
bool* aEventWasProcessed)
{
// This is only supposed to be called from the thread itself so it's not
// implemented here.
NS_NOTREACHED("Shouldn't ever call this!");
return NS_ERROR_UNEXPECTED;
}
NS_IMETHODIMP
LazyIdleThread::Notify(nsITimer* aTimer)
{
ASSERT_OWNING_THREAD();
{
MutexAutoLock lock(mMutex);
if (mPendingEventCount || mIdleNotificationCount) {
// Another event was scheduled since this timer was set. Don't do
// anything and wait for the timer to fire again.
return NS_OK;
}
}
nsresult rv = ShutdownThread();
if (NS_WARN_IF(NS_FAILED(rv))) {
return rv;
}
return NS_OK;
}
NS_IMETHODIMP
LazyIdleThread::OnDispatchedEvent(nsIThreadInternal* /*aThread */)
{
MOZ_ASSERT(NS_GetCurrentThread() == mOwningThread, "Wrong thread!");
return NS_OK;
}
NS_IMETHODIMP
LazyIdleThread::OnProcessNextEvent(nsIThreadInternal* /* aThread */,
bool /* aMayWait */)
{
return NS_OK;
}
NS_IMETHODIMP
LazyIdleThread::AfterProcessNextEvent(nsIThreadInternal* /* aThread */,
bool aEventWasProcessed)
{
bool shouldNotifyIdle;
{
MutexAutoLock lock(mMutex);
if (aEventWasProcessed) {
MOZ_ASSERT(mPendingEventCount, "Mismatched calls to observer methods!");
--mPendingEventCount;
}
if (mThreadIsShuttingDown) {
// We're shutting down, no need to fire any timer.
return NS_OK;
}
shouldNotifyIdle = !mPendingEventCount;
if (shouldNotifyIdle) {
MOZ_ASSERT(mIdleNotificationCount < UINT32_MAX, "Way too many!");
mIdleNotificationCount++;
}
}
if (shouldNotifyIdle) {
nsCOMPtr<nsIRunnable> runnable =
NewRunnableMethod(this, &LazyIdleThread::ScheduleTimer);
if (NS_WARN_IF(!runnable)) {
return NS_ERROR_UNEXPECTED;
}
nsresult rv = mOwningThread->Dispatch(runnable.forget(), NS_DISPATCH_NORMAL);
if (NS_WARN_IF(NS_FAILED(rv))) {
return rv;
}
}
return NS_OK;
}
NS_IMETHODIMP
LazyIdleThread::Observe(nsISupports* /* aSubject */,
const char* aTopic,
const char16_t* /* aData */)
{
MOZ_ASSERT(NS_IsMainThread(), "Wrong thread!");
MOZ_ASSERT(mShutdownMethod == AutomaticShutdown,
"Should not receive notifications if not AutomaticShutdown!");
MOZ_ASSERT(!strcmp("xpcom-shutdown-threads", aTopic), "Bad topic!");
Shutdown();
return NS_OK;
}
} // namespace mozilla